Prebbles
Planting for timber and shelter in Otago
When John and Heather Prebble bought their farm at Mt Blue, Dunback, in
East Otago around 30 years ago, there weren’t too many trees
in the landscape. The urgent priority was to establish a buffer against
the notorious nor-westers, and the next five years saw nearly 3.2 km of
shelterbelts planted to protect stock, crops and their home. Later the
emphasis moved to timber production – today there’s
over 30ha of woodlots, including radiata, macrocarpa and
eucalyptus as well as poplars planted for fodder.
The landscape has been softened and tamed by the plantings, and the
gentle rural outlook is now a picture postcard of the farm forestry
model in action… trees planted for all the right reasons,
enhancing a productive livestock operation.
John and Heather now lease the farm to their son Mark, but their vision
and goals for the land haven’t changed over the decades.
John is very clear about his farming philosophy, driven by his
over-riding goal to develop a sustainable farming system that takes
account of the climatic conditions:
- To farm the property in a sustainable manner using inputs in relation to carrying capacity
- To look after the soils by disturbing them as little as possible, with maximum use of direct drilling
- To produce quality stock and get satisfaction from farming, and
- To produce satisfactory financial returns.
And he’s adamant that planting trees has played a vital role
in enhancing the farm’s performance.
Land description
The farm totals some 631 hectares, with soils comprising Claremont on
the downs and limestone on the hill country.
Altitude
ranges from 61m asl up to 471m asl, from
the flats and rolling
downs to steeper hill country. Approximately 160ha of developed,
rolling to steep downs planted in modern pasture grasses are fenced
into 23 paddocks, and around 440ha of over-sown and top-dressed tussock
country are fenced into 6 [now 8?] blocks. There’s also a 31
ha quarry and lime works on the property.
Despite frequent dry spells no irrigation is required, with sufficient
stock water available from county schemes and the farm’s own
springs.
[farm map]
Climate
Temperature is described as a “moderate” 30+
degrees in summer, with frosts in winter.
Rainfall averages 650mm, unevenly spread, with yearly totals ranging
from 500mm – 1000mm. A dry summer period can be expected most
years, with the occasional severe drought, and it’s rainfall
that dictates the carrying capacity of the property, with a tendency to
carry conservative stock numbers.
Farm Operation
The farm now runs 1750 ewes and 400 hoggets plus 75 beef cows and
winter calves for sale in spring.
Brassicas swedes, turnips, kale and rape
– are planted for summer lamb feed and winter feed. All crops
are direct drilled where possible, although some conventional sowing is
still done depending on circumstances.
The many roles of trees
Trees were initially planted to provide shelter to enhance the
property, with woodlots for profit sited to make maximum use of poorer
land and also to provide shelter. All up over 34ha of woodlots,
including radiata, macrocarpa and eucalyptus, have been planted over
the years, along with 3.2km of shelterbelts and 1.5ha of fodder poplars.
Shelter
Having planted
around 3.2 km of shelter belts as one of his first
priorities on taking over the farm, John Prebble just shakes his head
when the subject of ripping out shelter for dairy conversions comes up.
He says although he hasn’t tried to quantify the benefits of
shelter on the property, the sheltered paddocks are now “the
best on the place”. Shelterbelts are a mix of P.
radiata/arizonica, Flevo poplars, P. muricata/arizonica planted in
1981-185 with some Leighton Green and Western Red Cedar planted in 1992
(Figure 1).
Figure
1: SHELTERBELT PLANTINGS
Visiting in November, with signs of a possible summer drought already
concerning the Prebbles, the shelter effect was obvious. The Tank
Paddock had been sown in kale two days previously. Whereas all the
other paddocks were “dry as a bone” according to
John, a quick probe with his pocket knife showed that this paddock,
virtually surrounded on four sides by shelter, still had moisture in
it. [shot of pocketknife and moisture]
“We’ve noticed in the last few years, particularly
during the last couple of dry autumns, this one is the only one with
any green on it left on the place,” he says.
Woodlots
All
told some 34 ha
of woodlots – mainly radiata and
macrocarpa, plus a small area of eucalyptus have
been planted for timber production, starting in 1989 and continuing
with annual plantings through to 1997 (Figure 2).
Figure 2: WOODLOT PLANTINGS
The oldest block, radiata pine planted in 1989, is now 20 years old and
the trees are growing well. Planted at 10 x 2 as an agroforestry block,
pruned at 4-5m and thinned to 240 sph, the GF22 trees are showing good
growth and form. This woodlot has a site index of 31 (307m3), which
John says is high for the district, the usual range being more like
25-31. Branching is quite fine, and there’s not a lot of
taper.
When the trees were about 15m it was particularly good shelter at
shearing time, although that advantage isn’t so great now
that the grass cover has reduced.
This block will be the first to be harvested, although that’s
some years off yet and (understandably) the Prebbles say they will be
interested to see what the log prices will be like then.
Meanwhile
they
have already experienced the practical realities of
harvesting, having sold some timber in 2006 after taking out a couple
of radiata shelter belts.
All up some 400t of logs were extracted, with a net return of around
$9,000. John says the best price for the sawlogs came from local mill
Hewvan Timber, realising 82t of S grade at $39 per tonne. The rest were
exported through Port Chalmers, a mix of Export A, K and K1 grades.
It was a
good price at the
time for the sawlogs, says John, although
tinged with some disappointment at the volumes. The Prebbles had
expected they would get 150m3 or more in sawlogs, but a lot of the
pruned logs just didn’t quite reach length specifications. It
was a good lesson learned.
“Being shelterbelts we hadn’t consciously pruned
them up to 6m and a lot of them were falling just that much
short,” recalls John. “It was just that last ring
of knots that was putting them out.”
An unexpected bonus was being able to recover timber from three poplars
that would otherwise have been smashed when the radiata was felled. The
contractor felled them and pulled the logs out into the paddock.
They’ve since been milled and treated for the top of a new
deck.
In the mid to late 90s the Prebbles carried out three joint venture
plantings, in partnership with ???. The joint venture structure brought
in useful cash flow that kept the planting momentum going [is this
true? need more here!].
Macrocarpas
Some of the Prebbles earliest woodlot plantings were
macrocarpas. Longwoods from Edendale Nurseries in
1989 and more Longwoods from Fords Nurseries in 1990.
The
onset of
canker in XXX had John scratching his head, until the
Prebble’s forestry advisor, Dave Pearson, of Plantation
Management Services came across an old article describing the use of
boron as a remedy for canker.
Cypress canker (Seiridium cardinale and S.unicorne) is widespread
throughout New Zealand, and can kill young trees. For those growing
cypresses for timber production the impact can be severe, with the
disease reducing returns due to malformations and stem cankers. The
usual strategy is one of prevention, managed by selecting the
appropriate species for the site. Unfortunately C. macrocarpa is
particularly susceptible to the disease, suffering branch and stem
dieback. (For more information click
here)
The decision was made to apply a tonne of boron, not only to the
macrocarpas but also to two small blocks of pines. The boron was
applied by helicopter in xxx 2008 [???], and within six months the
change was dramatic.
The trees have gone from what John describes as a “sickly
yellowy-green” to a better, healthier green and the canker
has seemed to not get any worse, he says John. He believes the boron
does seem to have controlled the disease, with only a few trees showing
lingering signs of yellowing. His plan is to let the stand stabilise
then thin out the affected stems and finish pruning the good trees.
Although the Prebbles did a lot of planting early on, woodlot planting
has virtually ceased in recent years so John can complete pruning and
thinning on the existing stands. He’s used contractors in the
past as well as doing a lot of the work himself, but says
he’ll finish doing the “tidying up”
himself. With son Mark now leasing the farm, John sees future timber
sales as an aid to succession planning, although any further planting
will most likely be more shelter.
Fodder
The
Prebbles’ interest in planting poplars for stock fodder
started back in 1989, when they planted 500 Flevo (P. deltoides x
nigra) wands supplied by the Otago Catchment Board. The 1.5 ha block
was established and managed purely as a way of feeding stock during
drought.
Reading the handbook Growing Poplar and Willow Trees on Farms, it seems
Flevo would not normally be regarded as the ideal species for sites
prone to mid-summer drought and has since been superceded by newer
clones. However it is recommended as a fodder resource because of its
large leaves and many branches.
In 1998, under severe drought conditions, 33 steers were fed 10 trees
every day, with results that have since been described as
“amazing” by the Ballance Award regional
co-ordinator Rhys Millar.
John says the cattle did do quite well, although they did damage the
trees. He only puts sheep in there now because cattle stripped the bark
off so badly. Last autumn he ran around 300 ewes in the block. The
trees have recovered quite quickly and are coming away again well, and
will be available to feed off in two years time.
In 2004 John
helped Barrie Wills of Central Environmental Services,
Alexandra, and land and forest consultant Murray Harris set up a trial
with a grant from the Sustainable Farming Fund (SFF Project #04/089) to
evaluate the effects of simple practical pruning treatments on tree
fodder production and possible leaf retention. The project looked at
quantifying dry matter yield and analysed the quality of the feed.
Well-placed fencing for maximum animal control during grazing is seen
as the key to good utilisation of tree fodder. The trial concluded that
autumn pruning produced greater biomass within the relatively short two
growing season period from pruning to harvest. Eliminating smaller
branches during pruning improved yield initially but was eventually
offset by a decrease in edible fodder. In his report on the project
Barry Wills says when trimming larger trees for the first time
horizontal cuts should be avoided, as it restricts wound healing and
meristem development (from which new branches arise).
The treatments applied to the trees had a negligible effect on leaf
retention at the end of the growing season and using combinations of
different poplar species or cultivars was seen as a more effective way
of extending the fodder supply.
In 2006 John and Heather received a special regional Ballance Award in
recognition of their work with the project.
